Speed-control system



June 14, 1927.

- Filed Jan. 12," 1924 1,632,682 w. SEIZ SPEED CONTROL SYSTEM FIELD CU/WVE/VT JL IF 2 Sheets-Sheet I lnx entor Walter- 5eiz,

June 14,1927. 7 1,632,682-

W. SEIZ SPEED CONTROL SYSTEM Filed Jan. 12, 1924 2. Sheets-Sheet 2 Ira/enter: Waiter S ei 2,

His 'At'tohne y.

Patented June 14, 1927.

UNITED STATES PA ENT OFFICE.

WALTERSEIZ, 0F BADENQ SWITZERLAND, Assrenon 'ro ENERAL ELECTRIC COM- mm, A CORPORATION or NEW roan.

SPEED-CONTROL SYSTEM.

Applicationfiled January 12, 1924, Serial No.685,781 and in Germany January 18, 1923.

My invention relates to speed control systems in which an induction motor is con-v catenated with a. commutator exciting machine, and has for its object the provision of means for controlling in a simple and eliective manner the magnitude or' the voltage injected into the secondary circuit of the motor by the commutator n'iachine.

It is well known that the speed of an induction motor may be controlled by injecting into its secondary circuit a variable voltage which forsubsynchronous operation is opposed to theslip voltage and for-super.-

syuchron'ous operation is in phase with the,

slipvoltage. It'flias been proposed to pro duc 'this variable voltage by concatenating with the' induction motor a commutator machine having its-' field windings connected to the slip ringsof-the main motorthrough an adjustable rheostat. This arrangement is ob ect on able in that the losses in the exciter circuit" are large, especially when the resistan'ce ofthe rheostatisseveral times larger than the reactance of the excitingwinding. The use of afrheostat in the enciter field circuit may be avoided by the use oi'a series tield winding but this'scheme'is in'ipractical because of the large andexpensive switching apparatus requirec. It is of course possible to use, in conjunction with an exciter field winding connecte'd'to the mainmotor slip Fin s throu h a11"adjustable' rheostat, an additional field winding for supplying, partof the field excitation of the eXciter thus redcing" the resistance losses'in the field circuit. This arrangement, however, makes it impossible to bring the motor up to near synchronousspeed because of the fact that due to the unregulated or fixed field winding of the commutator machine, there is always produced a voltage opposed to the slip voltage to overcon'ie this difiiculty by so associating the regulated and unregulated field windings of the commutator machinejthat, throughout a part of the range of'operation' at least, I, the fluxes which theyproduce are opposed. With this'arrangement the voltage of the commutator machine may be reduced to zero 4 simply by increasing the flux or the regulatedfield winding until it is equal to that of the unregulated field windin My invention will be'better un erstood on reference to the following description when of the main motor; I propose considered in connection with the accompanying drawing and its scope will be point-- ed out by the appended claims. 7

'Referring now to the drawing, Figs. 1 audit are diagrams illustratii'ig certain operating characteristics oi -a speed control systenrin which my invention has been embodied; Fig. '3 shows a system in which my invention has been embodied; and Fig. 4 shows a modification thereof.

F 3 shows an induction. motor having its primary winding connected to a polyphase source of current 2 and its secondary winding connected through slip rings 3 to a regulating machine provided with a commutator winding l, compensating windings 5, series field windings 6 and shunt field windings 7f connected to the slip rings 3 through an adjustable resistor S and revereing switch 9.

Fig.4; shows a system which differs from that shown by Fig. 3 in that the series field windings 6 are replaced by delta-connected field windings 10 connected to the slip rings 3 through reactors 11, the purpose oi. which will be subsequently explained.

If, in Fig. 3, the fixed or unregulated field windings 6 are wound to supply only a part,

for example onehalt, of the total flux of the machine, the regulated field winding 7 is required to supply a flux; eitherto a st or oppose that of the unregulated field w1nding'ti, depending on the speed desired, and the switch 9 must therefore be provided for reversing its connections. Under these conditions the maximum current of the winding 6 will be comparatively small as will be apparent-on reference to Fig. 2 in which slip isplotted as abscissae and field current as ordinates, the various values of the current of the field winding 7 being indicated by the curve 1,, those of the field wii'iding 6 being represented by the curve I the actual losses in the rheostat 8 being indicated by the curve V, the losses which would occur in the rheostat 8 in the absence of the wind- -V readily shows that the ohmic losses of the regulated field winding are materially reduced by the differential arrangement of the windings 6 and 7 and thatthe field cur- 'ing 6 being indicated by the curve V and rent required to be carried by the winding 7 may, when the fixed winding is designed to produce only half the total flux, be re duced to one-half its maximum value when the fixed winding is omitted.

Fig. l diilers from Fig. 2 in that it shows the ciinditions which obtain when the windings (3 and '7 are dilierentially wound and are each designed to produce a flux equal to the total flux of the comn'iutator machine. It will be observed from curves V and V that in this case, while the maximum current I, of the field winding 7 is equal to the total exciting current l of the machine, the ohmic losses of the regulated field circuit are much less than they would he were the winding 6 omitted. For large slips these losses are also considerably less than in the case where the winding (i is designed to produce onehalf the total flux oi the machine. The w iding 6 may oi course be designed to produce any desired percentage of the total flux and the smallest ohmic loss in the regulated field chcuit thus be obtained at the speed at which the motor is most commonly opcrated.

While the winding 6 has been referred to as the fixed or unregulated field winding, it should be understood that if desired the flux produced by this winding may be regulated or reversed and smaller changes in flux be produced by manipulation of the rheostat in circuit with the winding 7. If the unregulated winding is connected as shown in Fig. 3, its flux will ot course vary with the slip of the main motor. At large slip therefore the flux produced by the fixed winding is smaller than at small slip when the secondary frequency is low. In accordance with my invention this disadvantage may be avoided by replacing the series field winding by a shunt field winding 10 connected to the slip rings of the main motor through reactors 11 as indicated in Fig. st. Under these conditions the fixed winding produces a flux of approximately constant value. the reactors serving to cut down the flux when the slip is high. The use of the shunt fixed winding also has the additional advantage that the speed may be adjusted with no load on the motor, whereas with the series field winding speed regulation can be etlected only when there is a load on the main motor.

It will be obvious to those skilled in the art that my invention may be used in connection with wel known means for power tactor correction, as for example by supplying an additional winding on the commutator machine, magnetically independent of the circuits of the main exciter windings, with current of suitable magnitude and phase, or by adjusting the phase relationship oi the currents in the regulated and unregulated windings in addition to the reg ulation required exclusively for speed regu' lation, but these arrangeniients, being old and well known, it is not necessary to describe them specifically.

I have explained my invention by illustrating and describing a certain specific embodiment thereof, but it will be readily understood by those skilled in the art that the invention may be embodied in many other forms than that shown and described. I, accordingly, do not wish to be restricted to the particular forms oi construction disclosed herein bv way of example for the purpose of setting forth my invention in accordance with the patent statutes. The terms of the appended claims are, therefore, not restricted to the precise structure disclosed, but are intended to cover all changes and modifications within the spirit and scope of my invention.

lVhat I claim as new and desire to secure by Letters Patent of the United States, is,

1. A speed control system wherein an induction motor is concatenated with a commutator machine for regulating its speed, characterized by the fact that said commutator machine is provided with regulated and unregulated exciting field windings as distinguished from compensating windings for producing opposed fluxes.

2. A speed control system coinprisiiig an induction motor, and a regulating machine concatenated with said induction motor for regulating its speed, said regulating machine being provided with an unregulated field winding arranged to produce flux in one direction and with a regulated field winding connected to the slip rings of said induction motor for producing a flux in the opposite direction.

3. speed control system comprising an induction motor, a commutator machine provided with regulated and unregulated field windings for producing opposed fluxes and concatenated with said induction motor for controlling its speed, means for regulating the flow of electricity in said regulated winding, and means connecting said regulated winding with the secondary circuit of said induction motor. I

4-. A speed control system con'lprising an induction motor, a commutator machine concatenated with said induction motor for controlling its speed and provided with regulated and unregulated field windings operatively associated with the secondary circuit of said induction motor for producing opposed fluxes, means lor adjusting the flow of electricity in said regulated winding, and means permanently associated with said regulating winding for rendering the flux which it produces independent of the slip of said induction motor.

5. A speed control system comprising an induction motor, a commutator machine conlie catenated with said induction motor for con- Winding, and a. reactor for rendering flow trolling its speed and rovided with reguof electricity in said unregulated Winding lated and unregulated eld windings'operaapproximately independent of the slip of 10 tivelyi associated with the secondary winding said induction motor. I 5 of said induction motor for producing op- In Witness whereof, I have hereunto set osed fluxes, a resistor for controlling the my hand this 20th day of December, 1923. Bow of electricity in said regulated field WALTER SEIZ. 

